Whoops! The NFL and Levi's Stadium grounds crew are preparing the stadium for Super Bowl 50, and there may have been a slight error in the original end zone paint jobs. Friend of the site Samuel Lam tweeted out this picture showing both end zones having the Denver Broncos logo. The near end zone is being painted in, and the far end zone shows the word Broncos, and their logo.
In discussing it, Sam brought up a good point. It is possible they were testing out some paint, and it was easier to paint over that, as opposed to the Panthers side of things. It is certainly possible this was done on purpose. It is also entirely possible this is a re-enactment of one of the greatest commercials of all time. Great googly moogly!